This invention relates generally to impact crushing machines, and more particularly, to impeller shoes for use in such machines.
Impact crushing machines are used to crush particulate matter, such as rock, into smaller aggregate material. In a vertical shaft impact crushing machine, particulate material is fed centrally downward through a feed tube and onto a horizontal impeller table assembly that is rotating about a vertical axis at a high speed. Impeller shoes mounted to the table assembly impact the particulate material and cause the particulate material to break into smaller aggregate material. The impeller shoes also cause the particulate material to accelerate radially outward from the table assembly at a very high velocity to impact against stationary anvil members positioned around the table assembly. When the aggregate material impacts the anvil members, the deceleration forces cause the aggregate material to further break apart into smaller pieces.
One of the principal concerns of operating impact crushing machines is the extensive wear of the parts in the crushing chamber, particularly, the impeller shoes. It is not unusual for impeller shoes to require replacement after 14 hours of operation. Frequent replacement of the impeller shoes imposes substantial costs, not only in the cost of the wear parts themselves but also the downtime for the equipment.
To increase wear life, various prior art impeller shoes have included pockets that collect crushed aggregate material during the crushing operation. The aggregate material in the pockets forms a surface that impacts the particulate material fed into the crushing machine and partially shields the impeller shoe. This aggregate-on-aggregate action is intended to reduce the wear of the impeller shoe.
One design for prior art impeller shoes is illustrated in FIG. 1, which shows an impeller table assembly 10 with the prior art impeller shoes 12 mounted thereon. The flow of aggregate material 14 between two impeller shoes on the table assembly as the table assembly rotates is shown by arrowed lines 16. Unfortunately, prior art pocket designs, such as that shown in FIG. 1, require moisture in the aggregate material 14 to improve the packing of the aggregate material 14 in the pockets. Without moisture, dry aggregate material does not fully pack in the pockets, thus increasing the exposure and subsequent wear of the impeller shoe. While moisture improves the packing of the aggregate material 14, it is also known that moisture adds to the abrasive characteristic of the aggregate material, thus defeating to a certain degree the benefit of including pockets in the impeller shoes 12. Furthermore, prior art pocket designs have limited the feed size of the particulate material to a smaller size due to the lighter weight and less-sturdy shape of the impeller shoe (i.e., compared to the feed size that a solid impeller shoe can handle).
What is needed, therefore, is an impeller shoe that incorporates pockets capable of packing crushed material without moisture and has the sturdiness and crushing capacities as such found in a solid impeller shoe. The impeller shoe of the present invention is directed to satisfy these needs and other deficiencies of the prior art.
The present invention is an impeller shoe comprising an elongated body of abrasion-resistant material. The elongated body of the impeller shoe extends longitudinally from an inner end to an outer end and has a pocket defined therein. The pocket has an open end at the front of the elongated body and two opposing sides extending transversely through the elongated body toward the back of the body. The two sides of the pocket are oriented substantially parallel to each other and set at an angle with respect to the back of the body in a direction toward the inner end. The pocket also has a substantially even width measured between the two sides through the length of the pocket.
An impeller shoe constructed in accordance with the present invention does not weigh substantially less than a solid impeller shoe and enjoys a sturdiness and crushing capacity greater than prior art pocketed impeller shoes. Moreover, the pockets are capable of fully packing with dry aggregate material during a crushing operation, and the impeller shoe maintains a wider wear pattern top to bottom over time as compared to prior art impeller shoes.
To further extend the wear life of an impeller shoe, the present invention also includes embedding one or more rods made of higher abrasion-resistant material, such as carbide or ceramic, in the impeller shoe. The rods are held in place by the material of the impeller shoe and are exposed when the outer material of the impeller shoe is worn away.